1. Field of the Invention
This invention generally relates to tactile panels, and more particularly, to a tactile panel that can prevent a decrease in a thrust force of a vibration panel and that can be assembled readily.
2. Description of the Related Art
FIG. 1 schematically shows a conventional tactile panel, also known as a haptic panel. FIG. 1 schematically shows a configuration of the conventional tactile panel, and is also an exploded perspective view of constructional members of the tactile panel. Referring to FIG. 1, a reference numeral 11 denotes an upper frame and a reference numeral 12 denotes a lower frame. Other members such as a vibration panel 13, as will be described later, are sandwiched and secured by the upper panel 11 and the lower panel 12 from top and bottom so as to form one unit.
A drive coil 14 is provided just below the vibration panel 13, and is bonded to the circumference of the vibration panel 13 as goes around the circumference thereof. A current is passed through the drive coil 14 to generate the thrust force in the vibration panel 13.
A rectangular shape of the vibration panel 13, to which the drive coil 14 is adhered, is secured by upper vibration panel holding members 15a and 15b from the top and by lower vibration panel holding members 16a and 16b from the bottom. The upper vibration panel holding members 15a and 15b and lower vibration panel holding members 16a and 16b are respectively arranged near rims of short sides of the rectangular shape of the vibration panel 13.
Immediately below the lower vibration panel holding members 16a and 16b, a pair of permanent magnets 17a and 17b are respectively provided on yokes 18a and 18b. Each of the permanent magnets 17a and 17b includes two permanent magnets, one of which has North Pole facing the vibration panel 13, and the other has South Pole facing the vibration panel 13. The panel is assembled by piercing bolts or the like on mounting holes 11a through 11d provided on four corners on the circumference of the upper frame 11 and mounting holes 12a through 12d provided on four corners on the circumference of the lower frame 12.
Generally, a soft elastic material such as sponge or rubber is employed in the vibration panel holding member of the conventional tactile panel so as not to decrease the thrust force of the vibration panel. Nevertheless, as far as the vibration panel is pushed and secured from top and bottom, the thrust force is inevitably absorbed by the vibration panel holding members every time the vibration panel vibrates up and down. This results in a problem in that the effective thrust force that contributes to the vibration is degraded.
Japanese Patent Application Publication No. 2001-333493 (hereinafter referred to as Document 1) discloses a plane speaker that does not disturb free vibrations of the vibration film. A crystal liquid polymer film is used for a material of the vibration film to suppress the expansion coefficient. A shock-absorbing sheet is attached to the pole face on the opposite side of the yoke of a permanent magnet to provide a gap between the shock-absorbing sheet and the vibration film. On the above-mentioned plane speaker, however, a set of the permanent magnet and the spiral coil are arranged almost uniformly on the vibration film. The structure thereof is different from that of the vibration panel shown in FIG. 1, which includes the tactile panel having the drive coil on the circumference of the vibration panel. Therefore, the technique disclosed in Document 1 cannot be applied to the prevention of the decrease in the thrust force of the vibration panel.
A pair of N pole and S pole of permanent magnets (and the yokes provided correspondingly) and the drive coil have to be arranged in a given positional relationship in order to give a given thrust force to the vibration panel. The configuration shown in FIG. 1, however, does not include a method of positioning the pair of permanent magnets. Thus, there arises another problem in that it is not easy to arrange the pair of permanent magnets at optimal positions and the assembling process also becomes complicated.